Jp’s Guide To Jeep Transfer Cases

Do all Jeep T-cases look the same to you? In the junkyard, did you ever mistake a Quadra-Trac for a rare aluminum Spicer 18? Are you as lost as Pee-wee Herman at a rodeo when it comes to identifying what T-case your Jeep left the factory with? Don’t know if your factory case is a keeper or junk; or where to get upgrades for it? If so, this guide may be worth keeping around in your garage or shop. We wish we had enough space to go into every little detail on every unit built, but we don’t. So, instead we picked those we thought were most important and put together this guide.

The Odd Ones
The following cases are less common and less popular for various reasons. These oddballs are not ideal for swaps due to their complexity or a problematic vacuum engagement system. All can be identified by a round tag on the rear portion of the case.

NV247J/ NP249: These cases came in ’93-’98 ZJ (NV249 Quadra-Trac) and ’99-’04 WJ (NV247J Quadra-Trac II). Each has a full-time 4WD system that automatically biased torque between front and rear axles. For the ’99 WJ, the NP247 “Quadra-Drive II” was introduced. The system used a gerotor pump to proportion torque through an internal clutch setup. When coupled with Jeep’s Vari-Loc axles (WJ only) the entire system was called Quadra-Drive instead of Quadra-Trac II. Unfortunately, NV247s can be problematic and expensive to repair and are not recommended as swap candidates.

NP219: Found in ’80-’82 full-size Cherokees and Wagoneers, the NP219 is based off the NP208. Comprised of a full-time 4WD chain-drive system with an aluminum case, the major difference between the NP219 and other models in the NP208 family is the lack of a vacuum-operated center differential.

NP228 and NP229: Found in ’80-’84 full-size Cherokees and Wagoneers, the NP228 and NP229 were based on the NP208 and feature the same exterior shell and chain-driven 4WD system. The only difference between the two is found in 4-Hi. On the NP228 the center differential will remain open in 4-Hi while the NP229 has a limited-slip differential to assist with high-range traction. Both units have differentials that will lock 100-percent when 4-Lo is selected and both feature a vacuum-operated center differential.

Spicer 18
The Spicer 18 is lightweight and employs a compact design that fits within the tight confines of smaller vehicles.

Identifying it: It is the only cast-iron Jeep T-case with both outputs on the passenger side. The PTO is on the back of the case and drives directly off the input gear. This unique arrangement allows fitment of PTO accessories or planetary overdrive units.

Variations: Thirty years of production allowed the Spicer 18 to see much refinement. Five major versions exist; early ’41-’45, ’45-’46; ’46-’55; ’55-’71; and ’66-’71. Early versions had a 1.97:1 low range, while the latter versions featured a 2.43:1 or 2.46:1 low range. With each new version came improvements to the size of intermediate shaft as well as upgrades to bearing design. Most early Spicer 18s came with twin-stick shifters from the factory, but many later models also employed single-stick shifters. The most sought-after version is found behind Buick V-6-powered CJs sporting T-86 or T-14 transmissions. This variant sports a 4.00-inch locating bore and a sturdier housing more akin to the Dana 20.

Pros/Cons: It’s strong for its size and the inline front and rear outputs simplify off-road driving by aligning the lowest hanging parts of the undercarriage—which is especially handy for rockcrawling scenarios. The downfall to the Spicer 18 is found in the design of the case. Under some extreme circumstances the case is known to crack between the intermediate shaft bore, the case bottom opening, or the PTO window. Due to the offset rear output design, some inherent power loss is unavoidable since all the engine power must transfer through the intermediate gear.

Dana 20
Some call the Dana 20 a perfected Spicer 18 because the cases share so many similarities. In fact, you can use a Dana 20 case with Spicer 18 internals to build a strong-case Spicer 18.The Dana 20 features a centered rear output and all are gear-driven, two-speed units with a cast-iron case. Jeep versions have a 2.03:1 low range. They have a four-position shifter that allows for 2WD; 4-Hi; Neutral; and 4-Lo. All are single-stick, but can be converted to twin-stick using aftermarket parts

Identifying it: The rear output shaft of the Dana 20 is in-line with the input shaft. Both units are very compact, so if you remember the input/output configuration, it’s easy to differentiate them from other Jeep cases.

Variations: Aside from Jeeps, the Dana 20 was also found in International Scouts, Ford Broncos, and even some Chevy Blazers. The Scout version is essentially the same as that of the Jeep, however the Ford model is quite noticeably different thanks to a driver-side front output. Additionally, the Ford version has a different mounting pattern that is not compatible with any popular Jeep transmissions. However, the Ford Dana 20s do have better 2.46:1 gears that can be swapped into the Jeep cases.

Pros/Cons: Measuring just 10.5-inches in length, this compact range box is hard to beat. In terms of strength, the Dana 20s are better than Spicer 18s but breakage is typically due to worn parts. We have seen the 10-spline rear output shaft snap on occasion, but usually because of inexperienced driving and torque spikes.

Aftermarket: Like the Spicer 18, many options exist in the aftermarket to improve the strength and functionality of the Dana 20. Advance Adapters offers a 32-spline rear output upgrade and TeraFlex sells a 3.15:1 low-range gearset, but the larger gears require a slight bit of case grinding to fit. Novak has billet-aluminum inspection pans and master rebuild kits available.

Dana 300
When the Dana 300 was built, Dana took everything learned from the Spicer 18 and Dana 20 to create the best light-duty transfer case available at the time. The cast-iron T-case is incredibly strong, but weighs just 85 pounds. Drive gears are helical-cut to minimize noise and the low range was a respectable 2.62:1.

Found in: ’80-’83 CJ-5; ’80-’86 CJ-7; ’81-’85 CJ-8. A different version was also found in the ’79-’80 International Scout. The Scout version featured the Spicer 18/Dana 20 “backwards Texas” bolt pattern and transmission-mounted input gear similar to the Dana 20 found in Scout vehicles.

Identifying it: Thanks to the smooth exterior finish of the cast-iron case, the Dana 300 is easy to spot. It’s larger than the Dana 20 and always has a passenger-side front output and a centered rear output with an aluminum tailhousing. The 23-spline input features a round six-bolt mounting face and all came with a single-stick shifter.

Variations: There are only two versions of the Jeep Dana 300. The ’80 version had a shorter (about 31⁄2-inch) rear output housing assembly. The ’81-’86 versions feature a longer output assembly (about 51⁄2-inch) to house provisions for the speedo used in CJs.

Pros/Cons: The Dana 300 was the last of the gear-driven Jeep transfer cases. The internal strength of this box is outstanding, but in stock form the rear output shaft is typically the first place where breakage will occur.

Aftermarket: TeraFlex offers a 4:1 low-range gearset, as does JB Conversions. You can also get 32-spline input and output shafts from JB Conversions and Advanced Adapters. Novak Conversions sells two versions of its billet-aluminum inspection pan to add additional fluid capacity. Clocking kits and twin sticks are sold through Advance Adapters.

The T-case is incredibly strong, but weighs just 85 pounds

Borg Warner 1305/1339 Quadra-Trac
This case superseded the Dana 20 and was only installed behind the AMC version of the TH400 automatic transmission. Both front and rear outputs are offset to the passenger-side like that of the Spicer 18 but the Quadra-Tracs are chain-driven. They’re not great candidates for swap projects. However, that shouldn’t take away from the fact that this transfer case was way ahead of its time. Prior to its introduction, no other Jeep transfer case had an all-aluminum case or was chain-driven. Additionally, the Quadra-Trac has a unique integrated limited-slip differential that transfers torque between the front and rear axles for full-time 4WD operation on all surfaces.

Identifying it: Thanks to the unique offset front and rear outputs, this case is easy to spot. The other dead giveaway is the huge, bulbous low-range gearbox of BW1339 models.

Variations: Two versions exist. The BW1305s are a single-speed, full-time T-case, while the BW1339s are basically a BW1305 with a 2.57:1 low-range gearbox bolted on the rear.

Pros/Cons: The Quadra-Trac transfer case has no provision for chain adjustment, so chain stretch can be a constant issue. With the factory clutch differential, they also required special fluid with friction modifier. These transfer cases are good for go-fast desert rigs, as the internal differential minimizes the effects of torque spikes at high speed.

Aftermarket: MileMarker used to offer a part-time conversion for these cases with a new chain and an optional overdrive ratio to reduce engine speeds. However, the overdrive version and chains are no longer available with the kits, so you’ll have to reuse the stock chain. Also, manufacturing is ceased, so the company is limited to its supply on hand. Due to the rarity of these cases and their limited production run, virtually no other aftermarket support exists nowadays and consumables are getting scarce. You can still get master rebuild kits from Novak Conversions.

New Process 208
This dual-range transfer case arrived on the scene in 1980. It featured a traditional 2WD, 4-Hi, Neutral, and 4-Lo arrangement. Used extensively in J-series pickups and full-size Cherokees, it was chain-driven with a planetary reduction in an aluminum case. All NP208s have a 2.61:1 low range.

Found in: ’80-’87 full-size Jeep Cherokee, Wagoneer, pickups

Identifying it: Like most New Process transfer cases, the NP208 has a round tag affixed to the rear case half. If the tag is missing, you can easily tell it apart from other aluminum-bodied cases because the rear case half has a smooth exterior with few support ribs. It has a driver-side front output and a larger-diameter tailhousing compared with most other models.

Variations: The architecture of the NP208 served as the foundation for numerous other New Process transfer cases. As such there are many comparable cases out there that share the same visual cues, but do not interchange with the Jeep-specific models. This can be a source of frustration. Also, GM had a version of the NP208 in K-series pickups, Blazers, and Suburbans from ’81-’86. This model employed a similar-looking, yet different circular mounting pattern than the Jeep NP208 and had a passenger-side front output. Like those found in Jeeps, Ford versions have a driver-side drop. Another version found in ’80-’87 Dodge Ramcharger, 1⁄2-, and 3⁄4-ton pickups used a passenger-side drop like GM. As for the NP208’s siblings, the NP219 was more complex and used a viscous clutch to direct torque. They were only available for two years before being replaced by the NP228/NP229 in 1982. Like the NP219, the NP228 and NP229 used a viscous clutch differential for full-time 4WD operation.

Pros/Cons: The NP208 family of transfer cases is plagued by thinly cast housings and is only ideal for stock power and torque applications. Bigger tires and aggressive driving will find the NP208’s case weakness quickly. The internals are pretty stout, but virtually nothing is available to beef up the weak cases.

Aftermarket: Aside from general rebuild kits, replacement parts, and different output yokes, accessorizing the NP208 is not possible.

New Process/New Venture Gear 231
First introduced in 1988 in the YJ, XJ, and MJ, the NP231 has a whole assortment of aftermarket support. This case is said to handle upwards of 1,600 lb-ft of torque in stock form.

Identifying it: Spotting the NP231 is easy thanks to the red and silver tag on the rear half of the case. If the tag is missing, you can also identify them by appearance; they have a distinctive six-bolt front mounting face.

Variations: Among variances of NP231s, the most important difference is input gear spline count. All four-cylinder, six-cylinder with Peugeot, and early AX15 transmissions were 21-spline. All other six-cylinder applications were 23-spline.Chevy and Dodge also used versions of the NP231. The GM version had a 27-spline input shaft and a five-bolt front face that is incompatible with the Jeep and Dodge six-bolt styles. Heavy-duty versions of the NP231 came in the ZJ and some Dodge pickups. These had a 1 1⁄4-inch chain and a more robust planetary compared to the standard 1⁄2-ton case.

Pros/Cons: The NP231 was engineered for durability and simplicity. However, off-road service life is typically less than that of a gear-driven transfer case because chains tend to stretch over time—especially when low range is used frequently. On the flipside, the NP231 is much quieter on the highway than a gear-driven model.

New Process 242
Introduced as the Selec-Trac in 1987, this chain-driven case was the replacement for the NP228. As such, the NP242 incorporates a torque-biasing feature. This allowed users a full-time 4WD option where engine torque could be split via an internal differential between the front and rear axles. This function would automatically bias traction where it was needed most. In full-time 4WD the case would bias 52-percent of torque to the rear output and 48-percent to the front. The unit could also be locked in part-time 4-Hi, 4-Lo, and 2WD as required.

Found in: ’87-’01 XJ; ’93-’98 ZJ; ’99-’04 WJ; ’02-’08 KJ.

Identifying it: The red and silver tag on the rear half of the aluminum case make it easy to spot. If the tag is missing you can also identify them quite simply by appearance. They have a unique-looking case casting with longitudinal ribs surrounding on the input side of the case. You can also tell the NP242 apart from other cases by looking inside the vehicle at the shift indicator. If the indicator has positions for “2WD, 4-part-time, 4-full-time, Neutral, 4-Lo,” it’s a NP242. If the shift indicator makes no mention of both 4-part-time and 4-full-time, it’s probably a different case.

Variations: Aside from the Jeep variant, GM offered a version of the NP242 in the Hummer H1 and H2. The GM models feature a stronger output shaft and a wider chain. The important thing to look for on a NP242 is the spline count of the input gear. The NP242 comes in 21- and 23-spline versions with long and short input gears. A rare medium- length input gear is found on ’93-’95 ZJs with the 46RE or the ’93 ZJ with the AW4 automatic behind the 4.0L I-6.

Pros/Cons: The NP242 was often blamed for poor fuel economy because drivers failed to understand which gear setting to use for a given driving scenario. Operation in part-time 4WD is not recommended on pavement because it tends to cause premature wear of drive components and tires. However, if you like having multiple options for mastering terrain types, the NP242 is a decent piece of gear.

New Venture 241 and 241OR
This photo shows both versions of the NV241. When the NV241OR (Rock-Trac) transfer case came out in 2003, the game suddenly changed. For the first time in Jeep’s history, you could get a 4:1 low-range ratio from the factory. Unfortunately, as a result, these cases command a hefty price tag and are hard to find used. The chain-driven NV241 also came in a non-OR version (left in photo) that had a 2.72:1 low range. Both versions featured a fixed rear output, an all-aluminum housing, a driver-side front output, and an integral three-wire vehicle speed sensor setup.

Identifying it: A quick look at the round ID tag located on the back half of the case will tell you if the NV241 you are looking at is indeed the coveted Rock-Trac model (it will have an “OR” after it). If no tag is present, you can still easily identify one by looking at the input side of the housing. Due to the 4:1 planetary the Rock-Trac has its own unique case that features additional overlap around the input assembly. This was required to house the larger planetary gears, and the rear case half has generous ribs to handle the increased torque afforded by the lower gearing.

Variations: Shown here are the only two Jeep versions that exist. Shown on the right is the Rock-Trac, which is known as the 241OR (OR stands for off-road). The non-Rubicon model is labeled 241J.

Pros/Cons: This Rock-Trac is largely regarded as one of the best swap options for many Jeep owners wanting a 4:1 chain-drive T-case. The high price tag is the only downfall to these stout units.

Aftermarket: Tom Wood’s Custom Drive Shafts offers conversion yokes and vehicle-specific driveshafts while Novak Conversions sells improved shift linkages. Advance Adapters has a cable shifter upgrade that works in stock applications and also makes swapping an NV241 into other vehicles a snap.

New Process 207
This chain-driven oddball introduced as the Command-Trac gets little attention due to its limited production run. Comprised of a spur-cut planetary setup housed in a two-piece cast-aluminum case, the NP207 was the predecessor to the NP231. It has a 2.61:1 low range as well as a driver-side front output. The single shifter allows for four possible operations: 2WD, 4-Hi, 4-Lo, and Neutral.

Found in: ’84-’87 XJ; ’87 YJ.

Identifying it: The NP207 is easily identified thanks to the round red and silver ID tag on the rear case half. Due to its rarity, you typically won’t find them in vehicles other than those listed above—they don’t make good candidates for swaps.

Variations: This transfer case comes in two different versions: 21- or 23-spline input. The 21-spline model is for the manual transmissions offered in the XJ/MJ (AX4/AX5) or the notoriously problematic five- speed (Peugeot BA-10/5). The 23-spline version came behind the TF904 automatic.

Pros/Cons: The NP207 has a wider chain than the NP231, but due to straight-cut planetary gears, tooth mesh is actually less than that of an NP231.

Aftermarket: Tom Wood’s Custom Drive Shafts has a slip yoke eliminator for the NP207 and master rebuild kits are available through many retailers.